The Statically Defined Tracing (SDT) provider creates probes at sites that a
software programmer has formally designated. The SDT mechanism allows programmers to consciously
choose locations of interest to users of DTrace and to convey some
semantic knowledge about each location through the probe name. The Solaris kernel
has defined a handful of SDT probes, and will likely add more
over time. DTrace also provides a mechanism for user application developers to
define static probes, described in Chapter 34, Statically Defined Tracing for User Applications.